Flow through system liquid membrane type electrode

ABSTRACT

A flow through system liquid membrane type electrode used for measuring a specific ion concentration in a flowing liquid sample. A cylindrical membrane holding member which is flat at one side surface, holds a sheet-like liquid membrane, the liquid membrane facing a liquid sample passage formed in a synthetic resin block, thereby to form a strong junction between the liquid membrane and the sample passage.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an improved flow through system liquidmembrane type electrode used for measuring a specific ion concentrationin a liquid sample while the liquid sample is flowing.

2. Description of the Prior Art

FIG. 1 shows an example of a conventional flow through system liquidmembrane type electrode, in which a liquid sample flow tube 13 extendsthrough a housing 12 having a cover 11, a communicating bore 14 isformed at the liquid sample flow tube 13, a liquid membrane 15 isconnected to the bore 14, an internal electrode 16 is mounted at apredetermined portion of housing 12, and an internal liquid 17 isenclosed in the housing 12. Such a conventional electrode is superior inhandling and provides in its flow tube 13 a liquid sample passage D,thereby being advantageous in that its assembly in liquid flow lines issimple and easy.

The smaller the diameter of passage D in the liquid sample flow tube 13,the more suitable the tube 13 for measuring a constituent in a verysmall sample, and the smaller the outer diameter of the liquid sampleflow tube 13, the more compact the electrode as a whole. Hence, a tubesmaller in diameter and thickness has hitherto been used as the liquidsample flow tube 13.

Therefore, the conventional electrode is extremely small in an area ofjunction between the liquid membrane and the communicating bore 14.Moreover, the face of the junction is curved and therefore difficult tojoin. Also, since the flow tube 13 is small in diameter, it has reducedstrength. It is not possible to intensively urge the liquid membrane 15against the bore so that it is strongly held thereto. As a result, thestrength of the junction between liquid membrane 15 and bore 14 is quitelow.

SUMMARY OF THE INVENTION

An object of the invention is to provide a flow through system liquidmembrane type electrode having a simple modification which raises thejunction strength of the liquid membrane so as to eliminate the defectin the conventional construction without negating the advantage of theconventional construction. The flow through system liquid membrane typeelectrode of the invention attains this object by providing a syntheticresin block having a space containing therein an internal electrode andan internal liquid, a passage for a liquid sample, and a cylindricalcommunicating space through which the liquid sample passage communicateswith the internal liquid containing space. A cylindrical membraneholding member is provided in contact with a liquid membrane on a singleflat surface at one side so as to face the liquid sample passage. A lidis provided for keeping the internal liquid in a sealed condition.

The electrode of the invention is superior in handling and ease ofassembly with respect to connection to the liquid flow line as is theconventional one, and also is provided especially with the membraneholding member such that the liquid membrane is joined thereto in onlyone plane, thereby enabling the junction strength of the liquid membraneto be extremely high. By providing the face of the junction in only oneplane, the area of the junction of the liquid membrane can be enlargedregardless of the diameter of the liquid sample passage, and themembrane holding member is made strong enough to withstand the pressureapplied thereto, whereby a junction strength much stronger than theconventional one is obtainable. Moreover, in spite of the largerjunction area, the liquid sample passage is reducible in diameter,thereby being suitable for measuring the constituents of a trace amountof liquid sample. Therefore, the flow through system liquid membranetype electrode of the invention, as a whole, while retaining theadvantages of the conventional one, has remarkably improved junctionstrength at the liquid membrane.

In a preferred embodiment of the invention, the boundry of the liquidsample passage is U-shaped in cross-section only at the portioncommunicating with the communicating space and is cylindrical at theother portions thereof. Thus, the area of the liquid membrane contactingthe liquid sample can be enlarged while the liquid sample passage isbasically cylindrical in cross section so as to facilitate manufacture.

Furthermore, an opening in the membrane holding member which providescommunication between the liquid membrane and the interior liquid isformed in an elongate slot coincident with the portion of the liquidsample passage having a U-shaped boundary to greatly enlarge the area ofliquid membrane thereby facilitating improvement of measuring accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will become more apparent inthe detailed description and examples which follow, when taken inconjunction with the accompanying drawings in which:

FIG. 1 is a sectional view exemplary of a conventional flow throughsystem liquid membrane type electrode;

FIG. 2 is a longitudinal section side view of a flow through systemliquid membrane type electrode in accordance with an embodiment of theinvention;

FIG. 3 is a longitudinal sectional view taken on line III--III in FIG.2; and

FIG. 4 is an exploded perspective view of a block and a membrane holdingmember in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 2-4, reference numeral 1 designates a body block madeof transparent synthetic resin such as acrylic acid resin which hasformed therein a space A for containing therein an internal electrode 2and an internal liquid (inner solution) 3, that is electrolyte solutionsuch as KCl, a liquid sample passage B of smaller diameter which extendsstraight and horizontally through block 1, and a generally cylindricalcommunicating space C through which the liquid sample passage Bcommunicates with the space A.

Since the block 1 is made of transparent synthetic resin, visualsupervision of flowing condition of the liquid can be done with ease.

Referring in detail to FIG. 4, the cylindrical space C has a circularflat base surface S₁. Part of liquid sample passage B which communicateswith the cylindrical portion C, has a boundary which opens upward intosurface S, and therefore is U-shaped in cross section and is larger thanother portions of passage B which are circular in cross section, thebase of the boundary of the U-shaped portion being continuous to thebase of the other portions.

Reference numeral 4 designates a cylindrical membrane holding memberhaving a flat bottom face S, which has an elongated slot b in face Sfacing and coincident with the open end a of the U-shaped portion ofpassage B in cylindrical space C and which has a bore 5 tapereddownwardly and communicating with the slot b. To the flat face Scovering the slot b is applied a liquid membrane 6 which is disclosed inJapanese Patent Application Laid Open Number 55-43488.

The membrane holding member 4 is mounted in the cylindrical space C inthe block 1 so as to bring the liquid membrane 6 into pressing contactwith the flat face S₁ at the bottom of the cylindrical communicatingspace C. In this position, liquid membrane 6 faces the liquid samplepassage B, thereby closing off the base of the cylindrical space C fromliquid passage B. The cylindrical side walls of membrane holding member4 are electrically insulated from the block 1 by a cylindrical layer ofresin material 18 such as silicon. The bottom surface of the space A isalso covered with a layer of insulating resin material 19 such assilicon.

A connector pin 7 extends through a side of block 1 into a cavity 20adjacent space A. A lead wire 8 passing through cavity 20 connects pin 7to internal electrode 2. Lead wire 8 is insulated from block 1 by afiller 22 made of resin material such as silicon which fills cavity 20.

Reference numeral 9 designates a lid for enclosing the internal liquid 3in space A and reference numeral 10 designates an O-ring provided in arecessed ring-shaped groove in a side wall of block 1 so as to surroundliquid passage B.

The slot b can alternatively be formed with other shapes for improvingthe measuring accuracy of the device.

While a preferred embodiment of the invention has been described indetail above, such description is for illustrative purposes only, and itis to be understood that changes and variations may be made withoutdeparting from the spirit and scope of the invention which is definedonly by the following claims.

What is claimed is:
 1. An electrode, comprising:a synthetic resin blockhaving a liquid containing space formed therein; an internal liquidcontained in said liquid containing space; an internal electrodecontained in said liquid containing space immersed in said liquid; astraight line sample passage extending entirely and straight throughsaid block for carrying liquid therethrough, having a continuousstraight boundary surface portion extending entirely through said blockand consisting of two cylindrical first sections having uniform equaldiameters and a second section between said two first sections; acommunicating space connecting said sample passage and said liquidcontaining space having a flat planar interior surface, said secondsection of said sample passage extending along said interior surface andhaving an outer periphery having a uniform, smooth, concavely archedcross section such that the furthest point in said cross section of saidsecond portion from the plane of said planar interior surface is adistance from said plane equal to said diameter of said first sections;a cylindrical membrane holding member fitted in said communicatingspace; a liquid membrane member held between said sample passage andsaid communicating space such that said liquid membrane member facessaid sample passage, blocking communication between said sample passageand said liquid; and a lid covering said liquid containing space so thatsaid lid and said block enclose said internal liquid.
 2. An electrode asin claim 1, wherein said cylindrical membrane holding member has aholding member passage therein providing communication between saidliquid membrane member and said internal liquid, said holding memberpassage terminating at one end at said liquid membrane member and withan elongated slot coincident with said second portion of said samplepassage.
 3. An electrode as in claim 2 wherein said holding memberpassage includes a conical bore converging from said liquid containingspace to said elongated slot.
 4. An electrode as in claim 3, whereinsaid resin block is transparent.
 5. An electrode as in claim 1, whereinsaid straight boundary surface is semicircular in cross section, saidfurthest point being located at the center of the semicircular arcdefined thereby.
 6. An electrode as in claim 1, wherein said block issubstantially box shaped, and rectangular in cross section.